1. Field of the Invention
The present invention relates to a cassette tape slack-preventing apparatus which is adapted for use in a magnetic recording/reproducing apparatus, such as a video tape recorder (VTR), wherein a capstan motor drives both a front loading mechanism and a tape-driving mechanism.
2. Description of the Related Art
As is well known, a helical scan VTR is provided with both a front loading mechanism and a tape-loading mechanism. When a video tape cassette containing a video tape is horizontally inserted into the cassette insertion port formed in the front face of the VTR, the front loading mechanism receives the cassette by means of a cassette holder and draws the cassette inside together with the cassette holder, and then lowers the cassette until it comes to the predetermined cassette-loading position. When the cassette is being lowered, its cover is opened, and the tape-pulling members of the tape-loading mechanism are inserted into the cassette and brought into contact with the inner side of the tape. Next, the tape-loading mechanism causes the tape-pulling members to pull the tape out of the cassette placed at the cassette-loading position and guides the tape such that it is in contact with about half of the circumference of the rotating cylinder. After the tape-loading mechanism sets the tape along the tape feed path in this way, various operation modes, such as recording, play, freeze (i.e., still image reproduction), slow play, fast-forward play, fast-rewind play, fast forward, and fast rewind, are selectively established with a mode-establishing mechanism and its associated circuits. If an eject key is operated, the tape-loading mechanism draws the tape back into the cassette, and the front loading mechanism returns the cassette from the cassette-loading position to the cassette insertion port.
With the recent trend toward miniaturization, it is demanded that the structural components of this type of magnetic recording/reproducing apparatus be simplified and reduced in both number and weight, without adversely affecting the ability to control the operation with high accuracy.
In a conventional VTR, the front loading mechanism for moving a tape cassette to the predetermined tape-loading position, the tape-loading mechanism for pulling the tape out of the tape cassette and bringing the tape into contact with the cylinder, and the tape-driving mechanism for driving the loaded tape are all driven or controlled by use of different motors specially designed for their respective purposes. Since each of these specially-designed motors can be controlled with high accuracy independently of the others, the operation of the driven-components of the VTR can be controlled with high accuracy. Due to the use of the specially-designed motors, however, the construction of the conventional VTR cannot be easily reduced in size or weight. It is therefore to difficult to manufacture a simple, light-in-weight VTR which meets the recent trend toward miniaturization.
Under the circumstances, it is thought to combine the front loading mechanism, the tape-loading mechanism and the tape-driving mechanism together in such a way that they can be driven or controlled by the same motor. If these mechanisms are combined in this way, the number of structural components can be reduced, so that a small-sized, light-in-weight VTR can be obtained.
Among various VTRs actually developed to date, there is a type wherein the capstan motor is used for driving both the front loading mechanism and the tape-driving mechanism (which includes not only a capstan shaft but also reel bases, etc.). This type of VTR operates as follows. The front loading mechanism moves the cassette to the predetermined loading position by utilization of the torque transmitted thereto from the capstan motor. Next, the tape-loading mechanism (which is driven by a motor different from the capstan motor, i.e., by a loading motor used for rotating mode cams) pulls the tape out of the cassette. Thereafter, the torque of the capstan motor is transmitted to the tape-driving mechanism (e.g., reel bases) in accordance with the user's operation.
In this type of VTR, the torque of the capstan motor is transmitted to the tape-driving mechanism (particularly, to the reel bases) whenever a driving force is transmitted to the front loading mechanism. This means that the tape take-up real of the real bases is rotated in the tape-winding direction when the front loading mechanism is operating. When the cassette has been loaded at the predetermined loading position (i.e., when the reel shaft-engaging hoes of the cassette have been brought into engagement with the reel shafts standing on the reel bases), the capstan motor is stopped, whereby the VTR is set in a standby condition, waiting for the user's next operation.
In the first state of the VTR (the first state being a state immediately after the cassette is loaded to the predetermined loading position), the tape take-up reel side of the cassette immediately stops since the capstan motor which drives the tape take-up reel is applied with a braking force during the first state. However, the tape-supply reel side of the cassette continues to rotate for some time, due to the moment of inertia, so that the tape is fed more than necessary, causing tape slack.
If tape slack is caused, the tape disengages from the slanted post and guide roller of the tape-pulling members, and thus drops. If the tape is pulled out of the cassette in this condition, it may happen that the tape will be brought into contact with the flanges of the slanted post and the guide roller, resulting in damage to the tape. It may also happen that the tape will fall in the gap between the chassis and the base member (by which the slanted post and the guide roller are supported), with the result that the tape may be stained with grease or cut. If the tape is stained with grease, this grease may attach also to the components of the tape-driving system, disabling the tape-driving system.
When, in the above-mentioned first state, the cassette is raised to return it to the cassette insertion port, the torque of the capstan motor is transmitted to the tape-supply reel in such a manner as to rotate the tape-supply reel in the tape-rewinding direction. If the tape is wound around the tape take-up reel at the time, the tape may slacken and overlap at the portions located inside the cover of the cassette.